Excel does not chain monthly returns, catch a sign-flipped denominator, or survive a broken workbook link the night before a client meeting. The workbook gives you an import-ready template plus the six return-math errors to check before you trust any spreadsheet number again.
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The workbook mirrors the importer's exact column layout, so what you fill in is what gets imported. No re-keying, no format guessing.
Entities, holdings, and month-end valuations, with the same headers the importer reads, dropdowns for the fields with fixed values, and notes on the rules that trip people up (month-end dates, ending values, name matching).
The smallest complete book: two entities, three holdings, three month-ends. Copy the shape with your two biggest entities and you have real numbers flowing in under an hour.
Six errors we find in hand-built portfolio spreadsheets, with the measured size of each and a test for yours. Two of them produce numbers that look perfectly plausible and are wrong.
Every portfolio spreadsheet starts as the correct decision. One entity, a dozen holdings, monthly statements keyed into a grid: Excel is the fastest tool for that job, and for a while the numbers are even right.
Then a trust gets added, then an IRA, then a private fund that reports quarterly on PDF. Someone makes a mid-year contribution and the since-inception return quietly stops meaning anything, because a spreadsheet that chains annual returns is off by whole percentage points once money moves mid-period. In our engine testing, annual chaining missed a true time-weighted return by 173 basis points at a 50% flow. The workbook's audit tab shows you how to test your own file for this and five other failures, including the one where an ABS() around a denominator hides a sign flip and reports a confident, wrong return.
You do not need to trust us on the math to get value from the audit: every check works on your spreadsheet as it stands today. And if the checks come back clean, you have lost nothing but ten minutes. If they do not, the rest of the workbook is the migration path, and our return-calculation guides show the formulas we use on the other side.
The workbook is free, the trial that follows is optional, and the download link keeps working even if you unsubscribe.
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